Furnace construction



June 21, R w CQGHILL 2,121,537

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R.- W. COGHILL FURNACE CONSTRUCTION Filed Dec. 29, 1952 3 Sheets-Sheet 3 INVENTOR BY 746W. 2., J

ATTORNE Patented June 21, 1938 UNITED STATES PATENT. OFFICE Alco Products, Inc., a

corporation of Delaware oplication December 29, 1932, Serial No. 649,298

Claims.

My invention relates to a furnace construction and more particularly to a tube still for use in processing hydrocarbon oils.

Tube stills have been widely used in recent 6 years for the processing of hydrocarbon oils. The tube stills which have been found to be very efficient generally consist of a casing having a firing chamber. A bank of tubes adapted to absorb the radiant heat developed from the firing chamber is placed therein. A bridge wall spaced from one end of the furnace serves to define a passageway in which a bank of tubes adapted to absorb the convection heat of 'the hot gases of combustion are placed. This construction is exemplified in many examples of the prior art. In the types of construction known, the hot gases of combustion must change direction causing turbulence. Then, too, as the hot gases give up their heat to the fluid being processed, their volume decreases. In order to compensate for this decrease in volume and maintain a uniform velocity or to obtain an increased velocity in the convection section, I propose to provide a construction in which the cross sectional area of the gas passage decreases in the direction of the flow of the combustion gases.

One object of my invention is to provide a still construction in which the hot combustion gases will have a substantially straight line flow, thus eliminating turbulence. I

Another object of my invention is to provide a still construction in which the gas passageway decreases uniformly in cross sectional area so that a converging passageway is formed to maintain the velocity of the combustion gases.

. Another object of my invention is to provide a still construction having a novel and efiicient manner of preheating the air going to my combustion chamber.

Another object of my invention is to provide a furnace with a setting exposed to radiant heat but permitting the uniform firing of said furnace over substantially the length of the tubes.

Another object of my invention is to provide a furnace construction having two radiant heat sections partially separated by a partition wall having independent burner controls so that the heat absorption in each radiant section maybe varied independently.

Another object of my invention is to provide a furnace construction having a double radiant heat section employing the convection gases generated in both sections in a common passageway in which the convection tubes are positioned.

Another object of my invention is to provide a novel furnace construction in which the convection heat section is independently supported above the radiant heat section.

Other objects of my invention will appear from the following description.

In the accompanying drawings which form part of the instant specification and which are to be read in conjunction therewith and'in which like reference numerals are used to designate like parts in the various views;

Figure 1 shows a perspective view of my furnace construction.

Figure 2 shows a sectional elevation of a furnace construction embodying one mode of carrying out my invention and showing one method of passing the fluid being processed therethrough.

Figure-3 is a diagrammatic view of a sectional elevation of a furnace embodying my invention showing another method of passing the 011 therethrough.

Figure 4 is a diagrammatic view of a sectional elevation of a furnace embodying my invention showing another method of passing the 011 therethrough.

In general my invention contemplates the provision of a furnace setting having in general an A-shaped or trapezoidal cross section with the base of the A at the lower portion so that the cross sectional area of a plurality of planes parallel to the base would decrease in an upward direction. The radiant heat absorbing tubes are positioned within the casing in the lower portion thereof. The convection heat section is likewise of a progressively decreasing cross section and is mounted above the radiant heat section in a casing which is supported independently of the radiant heat section casing by means of girders or the like exercising thrust directly against the ground. Above the convection heat section I provide an air preheater adapted to heat the air used for combustion in the combustion chamber by heat exchange with the combustion gases 'goingto the stack. If desired, I may provide a partition wall at the lower part of my casing to divide it into two sections. These sections may be independently fired.

More particularly referring now to the drawings, the furnace casing I which may be of any suitable construction, is provided with inclined side walls 2. A partition wall 3 may divide the casing l into two sections, as can be readily seen by reference to Figure 2. The sections have suitable heat generating means such as oil burners t and 5. If desired, auxiliary burners 6 and I may be employed. While I have shown an oil burning furnace, it is to be understood that, if desired, a coal or gas burning furnace may be used. The walls of the furnace casing are lined with tube banks 8 and 9, adapted to absorb the radiant heat generated. Likewise, the fioor of the furnace is provided with radiant heat absorbing banks In and II as are the partition wall sides with tube banks l2 and IS. The tube banks 8., l0, and i2 are connected in series as can be readily seen by .reference to Figure 2 to form a radiant heat absorbing section on one side of the partition wall 8. Likewise, the radiant heat absorbing elements 9, H, and I3 are connected in series to form another radiant heat section on the opposite side of the partition wall as can be readily seen by reference to Figure 2. A secondary casing 20 is positioned above the main casing I. This casing is supported by any suitable construction by means of a plurality of girders 2| and 22, directly from the ground. The girders may terminate in suitable concrete piles 23 and 24. The sides of the secondary or convection section casing 20 are provided with converging side walls 25- and 26. A bank of convection tubes 21 is positioned in the convection section. This convection section is adapted to receive the hot products of combustion coming from both the radiant heat sec- -Spaced from the sides of the main casing I, I

provide sheathing 50 and 5|. It will be observed that the walls 2 of the furnace casing l and the sheathing 50 and 5| form jackets 52 and 53. The lower ends of these jackets communicate to the burners 4 and 5 and supply air thereto. Air is fed to the jackets 52 and 53 from a pair of ducts 54 and 55 connected with suitable air preheaters 40. Air enters a suitable intake 55 which may be equipped with a blower (not shown) for forced draft and passes through heat exchanger 40, through duct 55, through jacket 53, to burner 4. The heat from the furnace walls 2 serves further to preheat the air passing through the jackets, as will be apparent from the above description. The side walls 2 of the main furnace I may be inclined to any desired angle. Depending upon the heat intensity in the combustion chamber, it may be found that it will be advantageous to use walls of curved construction or several angles rather than a single plane surface.

In operation the hydrocarbon oil being processed may be introduced through suitable charge lines 50 and 10 to the convection bank 21 which may be split into two independent adjacent banks and flow downwardly through small combination convection and radiant heat banks GI and H through cross connections 62 and 12 to the radiant heat banks l3 and I2. It is to be understood, of course that the cross connections 62 and 12 may be placed without the furnace if desired. The type of flow now being described is illustrated in Figure 2 of the drawings. After passing through radiant heat tubes l2, l0, and 8, the oil which was charged at 10 may be withdrawn through pipe 13. The oil which was charged to pipe 50 will pass through radiant heat tubes [3, H, and 9, and be withdrawn through pipe 83. With this type of fiow, the

independent firing points 4 and 5 may be regulated to maintain different temperatures in each radiant section depending on the type of process desired. It will be noted that in general the direction of fiow of the oil being processed is concurrent in the radiant heat bank and counter-" current in the convection bank in the-form of construction shown in Figure 2.

Inthe form oLconstruction shown in Figure 3,

-I may charge one stream through the entire upper section of the convection bank and the other stream through the entire lower section of the convection bank as can be readily seen by reference to the figure. In this form of construction I am enabled to charge two different stocks each having a different inlet temperature and fire them to independent outlet temperatures.

Another form of construction is shown in Figure 4 in which the direction of oil flow is indicated by the arrows. It is countercurrent in the convection section and both countercurrent and concurrent in the radiant heat section.

It is to be noted in my construction that the tubes of the radiant bank and the convection sections are parallel to each other so that substantially no change in the direction of the flow of the fiue gas need take place.

It will be readily appreciated that my construction has many advantages. I am enabled to obtain a straight line flow of combustion gases .and eliminate turbulence. I am enabled to maintain a uniform speed of fiow or obtain an increased speed of fiow of the combustion gases in the convection section. I employ the heat generated in the combustion chamber to the maximum advantage by preheating the air and absorbing the heat from the furnace walls in my jacket'construction. I am enabled to pro- .vide a flexible control in processing difierent types of hydrocarbon oils.

It will be understood that certain features and sub-combinations are of utility and may be 'employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of my claims. It is further obvious that various changes may be made in details within the scope of my claims without departing from the spirit of my invention. It

is, therefore, to be understood that my invention is not to be limited to the specific, details shown passageway for conducting the hot combustion for conducting the hot combustion gases of both radiant heat sections to the atmosphere without substantial change in direction and convection tubes positioned within said passageway above said radiant heat tubes.

3. A tube still for processing hydrocarbon oils, including in combination a furnace setting, a partition wall Within said setting forming a plurality of combustion chambers with said setting, a common combustion gas passageway formed by said setting above said chambers, a bank of tubes adapted to be heated mainly by radiant heat disposed within said setting at one side of said partition Wall, a second bank of tubes adapted to be heated mainly by radiant heat disposed within said setting at the opposite side of said partition wall, a bank of tubes adapted to be heated mainly by convection heat disposed in said passageway and connected to one of said radiantly heated banks, a second bank of tubes adapted to be heated mainly by convection heat disposed in said passageway and connected to the other of said radiantly heated banks, and

means for separately charging incoming oil to said convection banks and separately removing outgoing oil from said radiant banks.

4. In a still for processing hydrocarbon oils having a setting having a progressively smoothly decreasing cross sectional area in the direction of the flow of the hot furnace gases, a housing for said setting positioned in spaced relation thereto, said housing and said setting adapted to form a jacket and means for passing air for the combustion chamber through said jacket.

.5. A still including in combination a setting having a progressively smoothly decreasing cross sectional area in the direction of the flow of the hot furnace gases, sheathing spaced from said setting externally thereof, said sheathing and said setting forming a jacket, means for preheating the air for the combustion chamber and means for passing the preheated air through the jacket to the combustion chamber.

ROBERT W. COGHILL. 

